The historian David Beddington said evangelicalism had 4 emphases: 1) The Bible 2) Christ and His Cross 3) Personal Conversion 4) Activism/Evangelism. Today some say that any group that makes an emphasis of those 4 things is by definition an evangelical. This is completely wrong headed.
What Beddington meant was that evangelicalism is a branch of mainstream/historic Christianity that emphasizes these things. In order words, evangelicalism is not a completely new form of Christianity that believes those 4 things, but it is a form of traditional Christianity that feels those 4 areas have been neglected and need to be reaffirmed.
Evangelicalism is a renewal movement within the stream of orthodox Christianity. It does not come along as a completely new form of the faith saying everyone else has been wrong till they came along. Instead, evangelicals have always been calling the traditional faith to new life through the 4 areas outlined above. They have not wanted to start a new faith but to bring the existing faith back to life. It is a revival movement within the mainstream, calling the mainstream to be renewed.
What is important to note about this, is that evangelicalism does not deny or change any doctrines of traditional Christianity. It brings a greater emphasis to certain doctrines within the mainstream tradition (see the 4 listed above) but it does not deny or change any orthodox doctrine that the church has always believed (at least the protestant church).Evangelicalism is completely and totally a subset of historic Christian belief. Its existence is dependent on the existence of the traditional faith. If the orthodox tradition of biblical Christianity ceases to exist, then evangelicalism would itself cease to exist.
This is important because some groups today want to claim to be evangelical while denying traditional Christian doctrines and ethics. For instance, some want to say God is not omniscient, that he does not know the future and yet these groups tclaim to be evangelical. The doctrine of the all knowing God has united all Christians, eastern orthodox, roman catholic and protestants, for centuries. But now some groups want to deny this doctrine but claim to still be evangelical because they emphasize the 4 things mentioned above. This will not work. Evangelicalism is a subset of the traditional faith. If you deny elements of the historic stream of Christianity, you have placed yourself outside of evangelicalism. This is also true of many wanting to deny traditional biblical teaching on human sexual practice. They wish to deny what has been universal teaching of the church across all branches and yet still say, “we are evangelical.” Emphasizing the 4 areas above does not make one an evangelical if you cut evangelicalism off from the historic and biblical faith.